"ValueExpression Map" of a JSF component

I'm storing value expressions in a JSF component with the f:attribute tag, e.g.:

<h:inputText ...>
  <f:attribute name="myId1" value="#{bean.prop1}" />
  <f:attribute name="myId2" value="#{bean.prop2}" />
  <f:attribute name="myId3" value="#{bean.prop3}" />
</h:inputText>

Is there a way to access all of those value expres开发者_JS百科sions programmatically? (without knowlegde of the names myId1, myId2,...)

Section 9.4.2 of the JSF 2.1 specification says that those values are stored "in the component’s ValueExpression Map". That's the only occurrence of the term "ValueExpression Map" in the complete spec. How do I access that map?

In the UIcomponent's Method getValueExpression() of the Jboss/Mojarra implementation the map

getStateHelper().get(UIComponentBase.PropertyKeys.bindings) 

is used to obtain a single value expression.

I guess that map is a super set of the "ValueExpression Map"? Can I be sure that all implementations and all inherited (standard) components use that map to store ValueExpressions?

Thanks.

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In theory you should be able to see them all by UIComponent#getAttributes():

Map<String, Object> attributes = component.getAttributes();

for (Map.Entry<String, Object> entry : attributes.entrySet()) {
    System.out.printf("name=%s, value=%s%n", entry.getKey(), entry.getValue());
}

However, that doesn't work the way as you'd expect. It only returns static attributes. This does not seem to ever going to be fixed/implemented. See also JSF issue 636. I'd suggest to stick to attribtues with predefinied prefix and an incremental numerical suffix, like as you've presented in your example. That's also what I've always used to pass additional information from the component on to custom validators and converters. You can just collect them as follows:

Map<String, Object> attributes = component.getAttributes();
List<Object> values = new ArrayList<Object>();

for (int i = 1; i < Integer.MAX_VALUE; i++) {
    Object value = attributes.get("myId" + i);
    if (value == null) break;
    values.add(value);
}

System.out.println(values);

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An alternative to the answer given by BalusC might be to use nested facets or UIParameter components. Facets can be retrieved as a map using getFacets but you probably need to put an additional UIOutput inside each facet to access its value expression.

Nested UIParameters can be accessed by iterating over the components children and checking for instanceof UIParameter. UIParameters have name and value attributes and so could be easily converted to a map.

I have used parameters in a custom component, but I'm not sure how a standard UIInput like in your example reacts to these.

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BalusC is right. UIComponent#getAttributes().get(name) gets values from both places - at first from attributes map and then if not found from "value expression map". To put some value you have to call UIComponent#setValueExpression(name, ValueExpression). If value is literal, it gets stored into the attribute map, otherwise into the "value expression map". Everything is ok then.